The present invention relates broadly to a spatial phase correlator apparatus, and in particular to a double pinhole spatial phase correlator apparatus.
In the prior art various techniques have been utilized to achieve spatial correlation. One known technique utilizes a partially coherent optical correlator which includes an adjustable slit that is used in producing a plurality of correlation samples which are added incoherently in an energy detector. Repeated scanning cycles are used to develop the full partially coherent correlation function. An additional attempt at correlation is through the use of a binary mask as an optical filter.
A partially coherent optical correlator has been developed in the prior art. It is formed by utilizing a non-coherent light source in place of the point light source, and condensing and collimating lenses and associated slits of a fully coherent optical correlator. An axially movable lens provides means for adjusting the coherence interval to optimize the correlator output in accordance with the amount of time-base distortion present in the received signal. This is accomplished practically by adjusting the position of a lens so that each point in the non-coherent source forms a circle of light of proper diameter on the signal plane, with adjacent circles overlapping each other. A total integration is performed by correlating over the diameter of each circle and summing all such correlations incoherently for all circles in the aperture. The present invention utilizes a double pinhole aperture with variable spacing between the pinholes.